A Comparative Quantum Chemical Study of a Novel Synthetic Prenylated Chalcone: High Accuracy of NMR C-13 GIAO-DFT Scaling Factor Calculations at the mPW91PW91/6-31G(d) Level of Theory

Abstract: Chalcones are important intermediates for the synthesis of biologically active compounds such as flavonoid and isoflavonoid and their derivatives. In one recent work quantum-chemical calculations were used for a better understanding of the NMR properties as well as for an analysis of the geometrical parameters in (2E)-1-(3,4-dimethoxyphenyl)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl)oxy] phenyl}prop-2-en-1-one, a novel compound. investigate our scaling factor protocol for NMR C-13 chemical shifts (delta) calculations at the mPW1PW91/6-31G(d)//mPW1PW91/6-31G(d) level of theory cost-effectiveness ratio (delta(scal) = -1.05 delta(calc)-1.22, where delta(calc) and delta(scal) are the calculated and the linearly scaled values of the C-13 chemical shifts, respectively). Hence we will compared our scaled NMR C-13 chemical shifts with the non scaled NMR C-13 chemical shifts obtained at the GIAO-DFT and GIAO-HF level of theory using 6-311++ G(d, p) basis set. Despite the calculation approximations, such as a truncated basis set, as well as the non-considered effects, such as solvent and rovibrational effects, the chemical shifts calculated at the mPW1PW91/6-31G(d)//mPW1PW91/631G( d) using a simple relationship (delta(scalc) = 1.05 delta(calc) -1.22 where delta(calc) and delta(scalc) are the calculated and the linearly scaled values of the C-13 chemical shifts, respectively) were able to yield MAD and RMS errors as small as those obtained with all DFT methods using bigger basis sets, 6-311++G(d,p).

Author(s): Costa, FLP; Mota, GVD; de Albuquerque, ACF; dos Santos, FM; de Amorim, MB

JOURNAL OF COMPUTATIONAL AND THEORETICAL NANOSCIENCE

DOI: 10.1166/jctn.2015.4008